1. Field of the Invention
The present invention relates in general to valves for mineral recovery wells, and in particular to actuators to actuate valves.
2. Brief Description of Related Art
A gate valve is a valve having a body and a bore through the body. A gate is positioned transverse to the body, and moves linearly to obstruct flow through the bore or allow flow through the bore. Some gates have an aperture that aligns with the bore to allow flow. The gate can be normally open, and thus the gate is closed when it is moved linearly to push the aperture out of alignment with the bore. Alternatively, a gate can be normally closed, and thus the gate is opened when it is moved linearly to position the aperture in alignment with the bore. Regardless of whether the gate is normally open or normally closed, the gate is moved, or actuated, by a valve actuator.
The valve actuator is a pneumatic, piston, or hydraulic type actuator that urges a stem toward the valve to either open or close the valve. A bonnet is connected to the valve, with the stem extending through the bonnet, and then the actuator is connected to the bonnet. Valve actuators are typically connected to the bonnet by threaded connections or by bolts through a flange. Threads are expensive to manufacture and are easily damaged. Machining bolt holes in the actuator and drilling and tapping holes into an adapter ring or the bonnet is expensive. Threaded connections also have the disadvantage that the inlet of the actuator rotates about the axis of the actuator during installation. If the actuator is fully tightened and the inlet ends up in the wrong location, the operating supply line to the inlet must be moved.